The invention relates to pipe lining. In pipeline systems it is known to line them with plastic pipe for refurbishment when corrosion puts the integrity of the existing pipe at risk or when a suitable barrier is required to prevent corrosion occurring. The existing host pipe may be steel, cast iron, asbestos or other rigid material. Polyethylene is typically used for the liner and provides a corrosion barrier for the oil and petrochemical industry for example.
To maximise the bore diameter it is preferred that the liner be a tight fit within the host pipe. An existing system utilises polyethylene piping which is forced through a die to compress its overall diameter as it passes in the pipe to aid insertion. Such a technique is employed in the Swagelinig (RTM) pipelining system.
There is established a number of other lining systems which when installed are not tight fit liners. This in turn means that there is an annulus between the liner pipe and the host pipe.
Where an annulus exists it is possible for substantial permeability to occur, which in turn can cause pressure balancing which could lead to implosion of the liner and consequential failure of the system.
With the Swagelining pipelining system, no annulus is present and permeability through the liner is thus greatly reduced.
The technical requirements for lined pipes may typically call for flanges every 500 meters which using non tight fit liners is achieved by drawing out the liner at each end of a lined pipe and butt fusing a polyethylene flange thereto; the line then being allowed to slip back within the host pipe. It has not been possible to deal with tight fit liners in this manner so as to allow flanges to be fitted.
The present invention is concerned with a mechanism for allowing flanges to be fitted to tight fit liners, typically polyethylene, within a host pipe.
According to the invention there is provided a method of lining a host pipe including the steps of: lubricating the host pipe along an internal face for an elongate portion at each end of the host pipe; lining the pipe with a thermoplastic liner using a tight fit technique; allowing the inserted pipe liner to relax; pulling a portion of the liner from the host pipe using limited force; affixing a thermoplastic flange thereto by a sealing technique; and allowing the liner to revert within the pipeline so as the thermoplastic flange abuts a flange on the host pipe.
Further according to the invention there is provided a puller device for pipe lining including fixing means for affixing the device to a rigid pipeline flange attached to a host pipe; gripper means for gripping a thermoplastic liner within the host pipe to allow a portion of the liner to be pulled from within the host pipe.
Separate means may be provided for holding the liner portion pulled from the pipe to allow the puller device to be removed and a thermoplastic pipe flange to be fitted prior to release of the liner.
Still further according to the invention there is provided a thermoplastic pipe flange including a first portion for butt fusion to a liner pipe and a second portion for affixing to a flanged portion of a rigid pipe.